A review of extreme condition effects on solder joint reliability:Understanding failure mechanisms

Solder joint,crucial component in electronic systems,face significant challenges when exposed to extreme conditions during applications.The solder joint reliability involving microstructure and mechanical properties will be affected by extreme conditions.Understanding the behaviour of solder joints under extreme conditions is vital to determine the durability and reliability of solder joint.This review paper aims to comprehensively explore the underlying failure mechanism affecting solder joint reliability under extreme conditions.This study covers an in-depth analysis of effect extreme temperature,mechanical stress,and radiation conditions towards solder joint.Impact of each condition to the microstructure including solder matrix and intermetallic compound layer,and mechanical properties such as fatigue,shear strength,creep,and hardness was thoroughly discussed.The failure mechanisms were illustrated in graphical diagrams to ensure clarity and understanding.Furthermore,the paper highlighted mitigation strategies that enhancing solder joint reliability under challenging operating conditions.The findings offer valuable guidance for researchers,engineers,and practitioners involved in electronics,engineering,and related fields,fostering advancements in solder joint reliability and performance.

Optimal Design of the Modular Joint Drive Train for Enhancing Cobot Load Capacity and Dynamic Performance

Automation advancements prompts the extensive integration of collaborative robot(cobot)across a range of industries.Compared to the commonly used design approach of increasing the payload-to-weight ratio of cobot to enhance load capacity,equal attention should be paid to the dynamic response characteristics of cobot during the design process to make the cobot more flexible.In this paper,a new method for designing the drive train parameters of cobot is proposed.Firstly,based on the analysis of factors influencing the load capacity and dynamic response characteristics,design criteria for both aspects are established for cobot with all optimization design criteria normalized within the design domain.Secondly,with the cobot in the horizontal pose,the motor design scheme is discretized and it takes the joint motor diameter and gearbox speed ratio as optimization design variables.Finally,all the discrete values of the optimization objectives are obtained through the enumeration method and the Pareto front is used to select the optimal solution through multi-objective optimization.Base on the cobot design method proposed in this paper,a six-axis cobot is designed and compared with the commercial cobot.The result shows that the load capacity of the designed cobot in this paper reaches 8.4 kg,surpassing the 5 kg load capacity commercial cobot which is used as a benchmark.The minimum resonance frequency of the joints is 42.70 Hz.

Microstructure,Corrosion and Mechanical Properties of Medium-Thick 6061-T6 Alloy/T2 Pure Cu Dissimilar Joints Produced by Double Side Friction Stir Z Shape Lap-Butt Welding

A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld microstructure and properties of DS-FSZW joint were systematically investigated.It indicated that defect-free medium-thick Al/Cu DS-FSZW joint could be achieved under an optimal welding parameter.DS-FSZW joint was prone to form void defects in the bottom of the second-pass weld.The recrystallization mechanisms at the top and middle of the weld nugget zone(WNZ)were continuous dynamic recrystallization(CDRX)and geometric dynamic recrystallization(GDRX).While the major recrystallization mechanism at the bottom of the WNZ was GDRX.DS-FSZW joint of the optimal welding condition with 850 r/min-400 mm/min was produced with a continuous thin and crack-free IMCs layer at the Al/Cu interface,and the maximum tensile strength of this joint is 160.57 MPa,which is equivalent to 65.54%of pure Cu base material.Moreover,the corrosion resistance of Al/Cu DS-FSZW joints also achieved its maximum value at the optimal welding parameter of 850 r/min-400 mm/min.It demonstrates that the DS-FSZW process can simultaneously produce medium-thick Al/Cu joints with excellent mechanical performance and corrosion resistance.

Shear mechanical properties and fracturing responses of layered rough jointed rock-like materials

This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading.Cubic layered samples with dimensions of 100 mm×100 mm×100 mm were casted using rock-like materials,with anisotropic angle(α)and joint roughness coefficient(JRC)ranging from 15°to 75°and 2-20,respectively.The direct shear tests were conducted under the application of initial normal stress(σ_(n)) ranging from 1-4 MPa.The test results indicate significant differences in mechanical properties,acoustic emission(AE)responses,maximum principal strain fields,and ultimate failure modes of layered samples under different test conditions.The peak stress increases with the increasingαand achieves a maximum value atα=60°or 75°.As σ_(n) increases,the peak stress shows an increasing trend,with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares fitting.As JRC increases from 2-4 to 18-20,the cohesion increases by 86.32%whenα=15°,while the cohesion decreases by 27.93%whenα=75°.The differences in roughness characteristics of shear failure surface induced byαresult in anisotropic post-peak AE responses,which is characterized by active AE signals whenαis small and quiet AE signals for a largeα.For a given JRC=6-8 andσ_(n)=1 MPa,asαincreases,the accumulative AE counts increase by 224.31%(αincreased from 15°to 60°),and then decrease by 14.68%(αincreased from 60°to 75°).The shear failure surface is formed along the weak interlayer whenα=15°and penetrates the layered matrix whenα=60°.Whenα=15°,as σ_(n) increases,the adjacent weak interlayer induces a change in the direction of tensile cracks propagation,resulting in a stepped pattern of cracks distribution.The increase in JRC intensifies roughness characteristics of shear failure surface for a smallα,however,it is not pronounced for a largeα.The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered rocks subjected to shear loads.

Dental Treatment Using Quantum Mechanics for Knee Joint Pain

In clinical practice, dentists sometimes encounter phenomena that cannot be explained by modern western medical concepts;for example, the patient’s medical symptoms improve by bringing medicines or dentures close to the body. Although it seems difficult to completely elucidate the mechanism through modern western medicine, it can be explained using quantum mechanics. The quantum, the smallest unit of matter composition, exhibits wave-particle duality. The fact that symptoms can be improved simply by bringing dentures or medicines closer to the body indicates that the waves emitted by dentures or medicines interfere with the pathological waves emitted by the pathological site. Thus, the pathological waves are deformed and lead to a change in symptoms. In this way, quantum theory can explain phenomena that are difficult to elucidate in conventional medicine, which are encountered in clinical practice. So far, the author has presented a case of difficulty in raising the upper limb where the symptoms improved without the need for dentures in the mouth by adjusting the dentures outside the mouth. This time, the author would like to introduce a case which the patient’s knee pain improved by adjusting the dentures outside the mouth.

Evaluation of the Effectiveness and Efficiency of Extracorporeal Shock Wave Combined with Rehabilitation Training in the Treatment of Muscle Articulation Chronic Pain

Objective: To analyze the effect of combined extracorporeal shock wave and rehabilitation training treatment in patients with muscle articulation chronic pain (MACP). Methods: Ninety-seven MACP patients admitted to our hospital from September 2021 to September 2023 were randomly selected and were divided into Group A (control group, 46 cases, rehabilitation training treatment) and Group B (observation group, 51 cases, extracorporeal shock wave with rehabilitation training treatment), and outcomes of the two groups were compared. Results: The treatment efficiency, post-treatment clinical indexes (upper and lower limb function scores, activities of daily living (ADL) scores, visual analog scale (VAS) scores), and short-form 36 (SF-36) scores of Group B were better than those of Group A (P < 0.05). Conclusion: Combined extracorporeal shock wave and rehabilitation training treatment for MACP patients improved their limb function, daily activities, quality of life, and reduced pain.

Mechanical characteristic and failure mechanism of joint with composite sucker rod

Composite sucker rods are widely used in oil fields because of light weight,high strength,and corrosion resistance.Bonded technology becomes the primary connection method of composites.However,the joints with composite sucker rods are prone to debone and fracture.The connected characteristics are less considered,so the failure mechanism of the joint is still unclear.Based on the cohesive zone model(CZM)and the Johnson-Cook constitutive model,a novel full-scale numerical model of the joint with composite sucker rod was established,and verified by pull-out experiments.The mechanical properties and slip characteristics of the joint were studied,and the damaged procession of the joint was explored.The results showed that:a)the numerical model was in good agreement with the experimental results,and the error is within 5%;b)the von Mises stress,shear stress,and interface stress distributed symmetrically along the circumferential path increased gradually from the fixed end to the loading end;c)the first-bonded interface near the loading end was damaged at first,followed by debonding of the second-bonded interface,leading to the complete shear fracture of the epoxy,and resulted in the debonding of the joint with composite sucker rod,which can provide a theoretical basis for the structural design and optimization of the joint.

Constraint and Mobility Change Analysis of Rubik’s Cube-inspired Reconfigurable Joints and Corresponding Parallel Mechanisms

The current research of reconfigurable parallel mechanism mainly focuses on the construction of reconfigurable joints.Compared with the method of changing the mobility by physical locking joints,the geometric constraint has good controllability,and the constructed parallel mechanism has more configurations and wider application range.This paper presents a reconfigurable axis(rA)joint inspired and evolved from Rubik’s Cubes,which have a unique feature of geometric and physical constraint of axes of joint.The effectiveness of the rA joint in the construction of the limb is analyzed,resulting in a change in mobility and topology of the parallel mechanism.The rA joint makes the angle among the three axes inside the groove changed arbitrarily.This change in mobility is completed by the case illustrated by a 3(rA)P(rA)reconfigurable parallel mechanism having variable mobility from 1 to 6 and having various special configurations including pure translations,pure rotations.The underlying principle of the metamorphosis of this rA joint is shown by investigating the dependence of the corresponding screw system comprising of line vectors,leading to evolution of the rA joint from two types of spherical joints to three types of variable Hooke joints and one revolute joint.The reconfigurable parallel mechanism alters its topology by rotating or locking the axis of rA joint to turn all limbs into different phases.The prototype of reconfigurable parallel mechanism is manufactured and all configurations are enumerated to verify the validity of the theoretical method by physical experiments.

Research of 6-DOF Serial-Parallel Mechanism Platform for Stability Training of Legged-Walking Robot

The concept of legged-robot stability training with a training platform is proposed and a serial-parallel mechanism platform with 6 degrees of freedom is designed for this target. The designed platform is composed of 4-DOF parallel mechanism with spherical joints and prismatic pairs,and 2-DOF serial mechanism with prismatic pairs. With this design,the platform has advantages of low platform countertop,big workspace,high carrying capacity and high stiffness. On the basis of DOF analysis and computation of space mechanism,weight supporting auxiliary mechanism and raceways-balls supporting mechanism are designed,so as to improve the stiffness of designed large platform and payload capacity of servo motors. And then the whole structure design work of the platform is done. Meanwhile,this paper derives the analytical solutions of forward kinematics, inverse kinematics and inverse dynamics. The error analysis model of position and orientation is established. And then the simulation is done in ADAMS to ensure the correctness and feasibility of this design.

Study on Talent Training Mechanisms of Marine Cultural Industry in China

In the 21 stcentury,countries in the world scramble to develop marine industry,and the sea is key to the improvement of core competence of a country. With the development of marine science and technology and marine industry,the construction of marine culture has been paid more attention to gradually at present. In China which has rich marine resources and long marine history and culture,marine cultural industry has been started late,but it has a vast development prospect. Along with the rapid development of marine cultural industry,shortage of talent in the industry has become increasingly serious and has become one of key factors limiting the development of the industry. In this study,based on the introduction of related concepts,problems of talent training in China's marine cultural industry were analyzed,and talent training mechanisms of marine cultural industry were proposed.

Study on Talent Training Mechanisms of Marine Cultural Industry Based on Collaborative Innovation of Governments,Enterprises,Colleges,Scientific Institutions and Users

Based on the review of related concepts,the current situation and problems of talent training in marine cultural industry in China were analyzed,and talent training mechanisms of marine cultural industry based on collaborative innovation of governments,enterprises,colleges,scientific institutions and users were proposed to promote the transformation,upgrading and vigorous development of marine cultural industry,accelerate the spread of marine culture with Chinese characteristics,and build China into a maritime power.

Research on the Construction of the Management Mechanism for Forestry Cadres' Education and Training

For the basic condition that the quality and efficiency of forestry cadres' education and training in China are not high at present, this paper first analyzes the necessity of constructing the management mechanism for forestry cadres' education and training from two aspects: improve the quality of forestry cadres' education and training and the inherent needs of forestry development, and also summarizes the existing problems in the management of forestry cadres' education and training in China at present, and finally, this paper puts forward the corresponding solutions from four aspects: strengthen macro planning, strengthen the construction of the quality supervision mechanism, reform the incentive system and safeguard the mechanism.

Construction of Early Warning Mechanism of Tourism Talent Training

The demand of tourism industry is the foothold and starting point of tourism talent training.How to adapt to the economic and social demand for tourism talent in the new era has become an important issue of The Times for tourism higher education talent training.By sorting out the research dynamics of talent training and industrial demand integration,the early warning mechanism of tourism talent training and industry demand is studied from the perspective of talent and industry integration.The early warning index system of tourism talent training and industrial demand is constructed using AHP method,and the problems existing in tourism talent training are found through real-time data observation and warning situation handling,thus providing decision-making support for the development of tourism management major in colleges and universities.

Research on Training Mode and Mechanism of Economic Management Talents of ＂Innovation-Entrepreneurship Type＂

Innovation is an inexhaustible motive force for the prosperity of a country. Only make full use of creative thinking, can society have a substantial development. Cultivating innovative and entrepreneurial talents for the society is an inescapable mission of colleges and universities. Entrepreneurship and innovation are conducive to China’s enterprises in many aspects of structural optimization. Talents with certain innovation ability can meet the requirements of social development. The colleges and universities are important bases for cultivating innovative talents which take it as a strategic task to cultivate innovation-entrepreneurship type talents. Nevertheless, most of the colleges and universities do not pay attention to innovation and entrepreneurship education and the teaching institutions should actively reform, and make full use of advanced information technology and train innovative talents. In this paper, we discuss the importance of training mode and mechanism of economic management talents with innovation-entrepreneurship type, and we put forward the direction of innovation and entrepreneurship education, at the same time, an innovative management mechanism should be established.

Research on the Tourism talents training mechanism of Poyang Lake Ecological Economic Zone

In order to promote the tourism development of Poyang Lake Ecological Economic Zone, to attract more customers, to build an effective personnel training mechanism, training professionals is very necessary. The advantages of Poyang Lake Ecological Economic Zone tourism development are introduced in this paper, and pointed out that the tourism talent training needs analysis of talent training status and improvement measures are proposed, including the integration of the region education resources, pay attention to the skilled personnel training, improve the teaching curriculum setting, improve the quality of Teachers, strengthen the construction of training base.

Responsibilities and Working Mechanism of National Human Rights Education and Training Bases

On July 22, 2014, the second group of national human rights education and train- ing bases was announced,increasing the number of national bases from the previous three to a total of eight, which reflects the advancement of human rights education and ~aining in China and has far-reaching significance.

Evaluation of microstructure and mechanical properties of squeeze overcast Al7075-Cu composite joints

Al7075-Cu composite joints were prepared by the squeeze overcast process.The effects of melt temperature,die temperature,and squeeze pressure on hardness and ultimate tensile strength(UTS)of squeeze overcast Al7075-Cu composite joints were studied.The experimental results depict that squeeze pressure is the most significant process parameter affecting the hardness and UTS.The optimal values of UTS(48 MPa)and hardness(76 HRB)are achieved at a melt temperature of 800℃,a die temperature of 250℃,and a squeeze pressure of 90 MPa.Scanning electron microscopy(SEM)shows that fractured surfaces show flatfaced morphology at the optimal experimental condition.Energy-dispersive spectroscopy(EDS)analysis depicts that the atomic weight percentage of Zn decreases with an increase in melt temperature and squeeze pressure.The optimal mechanical properties of the Al7075-Cu overcast joint were achieved at the Al2Cu eutectic phase due to the large number of copper atoms that dispersed into the aluminum melt during the solidification process and the formation of strong intermetallic bonds.Gray relational analysis integrated with the Taguchi method was used to develop an optimal set of control variables for multi-response parametric optimization.Confirmatory tests were performed to validate the effectiveness of the employed technique.The manufacturing of squeeze overcast Al7075-Cu composite joints at optimal process parameters delivers a great indication to acknowledge a new method for foundry practitioners to manufacture materials with superior mechanical properties.

Fracture behaviors of columnar jointed rock mass using interface mechanics theorem

For a special geological structure of columnar jointed rock mass(CJRM),its mechanical properties are strongly affected by the columnar joints.To describe the fracture behaviors of CJRM using the basic theories of interface mechanics for composite materials,the interface stresses of the vertical and horizontal joints,which are the two primary joints in the CJRM under triaxial compression,are studied,and their mathematical expressions are derived based on the superposition principle.Based on the obtained interface stresses of the vertical and horizontal joints in the CJRM,the crack initiation of the joint interface in the CJRM is studied using the maximum circumferential stress theory in fracture mechanics.Moreover,based on this investigation,the fracture behaviors of CJRM are analyzed.According to the results of similar material physical model tests for the CJRM,the theoretical study is verified.Finally,the influence of the mechanical parameters of the CJRM on the joint interface stress is discussed comprehensively.

Energy evolution mechanism and failure criteria of jointed surrounding rock under uniaxial compression

The object of this article is to investigate the energy evolution mechanism and failure criteria of cross-jointed samples containing an opening during deformation and failure based on the uniaxial compression test and rock energy principle.The results show that the energy evolution characteristics of the samples correspond to a typical progressive damage mode.The peak total energy,peak elastic energy,and total input energy of the samples all first decrease and then increase with an increase of half of the included angle,reaching their minimum values when this angle is 45°,while the dissipated energy generally increases with this angle.The existence of the opening and cross joints can obviously weaken the energy storage capacity of the rock,and the change in the included angle of the cross joint has a great influence on the elastic energy ratio of the sample before the peak stress,which leads to some differences in the distribution laws of the input energy.The continuous change and the subsequent sharp change in the rate of change in the energy consumption ratio can be used as the criteria of the crack initiation and propagation and the unstable failure of the sample,respectively.

Interactive Training Model of TRIZ for Mechanical Engineers in China

Abstract： Innovation is a process of taking an original idea and converting it into a business value, in which the engineers face some inventive problems which can be solved hardly by experience. TRIZ, as a new theory for companies in China, provides both conceptual and procedural knowledge for finding and solving inventive problems. Because the government plays a leading role in the diffusion of TRIZ, too many companies from different industries are waiting to be trained, but the quantity of the trainers mastering TRIZ is incompatible with that requirement. In this context, to improve the training effect, an interactive training model of TRIZ for the mechanical engineers in China is developed and the implementation in the form of training classes is carried out. The training process is divided into 6 phases as follows： selecting engineers, training stage-l, finding problems, training stage-2, finding solutions and summing up. The government, TRIZ institutions and companies to join the programs interact during the process. The government initiates and monitors a project in form of a training class of TRIZ and selects companies to join the programs. Each selected companies choose a few engineers to join the class and supervises the training result. The TRIZ institutions design the training courses and carry out training curriculum. With the beginning of the class, an effective communication channel is established by means of interview, discussion face to face, E-mail, QQ and so on. After two years training practices, the results show that innovative abilities of the engineers to join and pass the final examinations increased distinctly, and most of companies joined the training class have taken congnizance of the power of TRIZ for product innovation. This research proposes an interactive training model of TRIZ for mechanical engineers in China to expedite the knowledge diffusion of TRIZ.