The properties of anti-seismic HRB400 steel bars with 25 mm diameter were systematically investigated. The results showed that the properties of the HRB400 reinforced steel bars had been greatly enhanced comparing wit...The properties of anti-seismic HRB400 steel bars with 25 mm diameter were systematically investigated. The results showed that the properties of the HRB400 reinforced steel bars had been greatly enhanced comparing with HRB335 steel bars, i.e. coordination of strength and ductility, strain-aging sensibility, low temperature impact toughness, weld ability and high strain low cycle fatigue. The ductile-brittle transit temperatures of hot-rolled and strain-aged steel bars were evaluated as –17 °C and ?8 °C respectively, and the low temperature impact toughness of HRB400 steel bars remains to be improved. Transmission electron microscopy (TEM) and electron diffraction showed little vanadium existed in ferrite as VN, most of which existed in pearlite as alloy cementite which resulted in the declination of impact toughness. Methods were suggested to improve the anti- seismic properties of steel bars.展开更多
Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and ste...Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.展开更多
A number of geotechnical analyses were carried out on selected carbonate rock samples from eight sites located in Egypt. This analysis was to assess the suitability of these rocks for building construction aggregate. ...A number of geotechnical analyses were carried out on selected carbonate rock samples from eight sites located in Egypt. This analysis was to assess the suitability of these rocks for building construction aggregate. The analyses included properties of uniaxial compressive strength, tensile strength, porosity, water absorption, and dynamic fragmentation. The success of building construction depends to a large extent on the availability of raw materials at affordable prices. Raw materials commonly used in the building industry include sands, gravels, clays and clay-derived products. Despite the widespread occurrence of carbonate rocks throughout Egypt, the low premium placed on their direct application in the building sector may be explained in two ways: firstly, the lack of awareness of the potential uses of carbonate rocks in the building construction industry(beyond the production of asbestos, ceiling boards, roof sheets and Portland cement); and secondly, the aesthetic application of carbonate rocks in the building construction depends mainly on their physical attributes, a knowledge of which is generally restricted to within the confines of research laboratories and industries. Thus this paper addresses the physical and mechanical characteristics of some Egyptian carbonate rocks, evaluating them for their suitability as building construction aggregates.展开更多
Concrete, as an essential construction material in the construction industry, is the main component of solid waste. To improve the strength and durability of concrete, some additives can be added into concrete to repl...Concrete, as an essential construction material in the construction industry, is the main component of solid waste. To improve the strength and durability of concrete, some additives can be added into concrete to replace parts of cement. Carbon fiber and silica powder are the most common additives. Under a series of experiments, the effects of temperature, carbon fiber and silica powder on the mechanical properties of concrete were studied under normal circumstances. In this paper, a conclusion on the effects was drawn up mainly through some experimental analyses, so as to discuss the effect laws and provide a reference to manufacture the concrete of high strength and properties.展开更多
The aim of this research was to find out whether the effect of chemical corrosion changes mechanical characteristics of surface layers of wooden construction elements. Degradation of the surface layers of wood was cau...The aim of this research was to find out whether the effect of chemical corrosion changes mechanical characteristics of surface layers of wooden construction elements. Degradation of the surface layers of wood was caused by chemical reactions of the basic substances of wood mass with compounds contained in antifire coatings. Fire retardants containing corrosive substances were often and repeatedly used in the Czech Republic on many wooden building constructions. This process of chemical corrosion is in practise called as ＂surface defibering of wood＂. This contribution presents standard and special experimental methods used for measuring the selected mechanical characteristics （compression strength, tension strength, bending strength, hardness and impact resistance） in the damaged surface layer of wooden construction elements. The material for experimental measuring was a construction element removed from a historical roof （ca 150 years old）. Mechanical characteristics of the surface layer of the defibered element were compared with the values measured in the deeper subsurface layer of non-damaged wood. The results of the experiments proved loss of cohesive strength and decrease of mechanical characteristics of wood only in a thin surface layer.展开更多
The paper summarises the results of a questionnaire survey that took place in January 2015 in order to assess the current and prospective standard of the qualification of human resources in machine construction compan...The paper summarises the results of a questionnaire survey that took place in January 2015 in order to assess the current and prospective standard of the qualification of human resources in machine construction companies in the Czech Republic. The questionnaire survey included 23 small machine construction companies （less than 50 employees）, 24 medium-sized machine construction companies （50-249 employees）, and 53 larger machine construction companies （250 and more employees）. The results of the survey indicated that almost one half （43%） of respondent machine construction company top management members planned to hire new employees this year. In addition, 50% of them confirmed their endeavour to keep the current headcount and a mere 7% of them specified problems that would lead to the dismissal of employees. However, what is bothering machine construction top management members is the lack of qualifications and practical experience of job seekers they have to deal with. The intention of the authors is to define the main reasons and propose possible solutions of this problem within human resource management in machine construction companies.展开更多
Two kinds of big sympodial bamboo, D.Yunnanicus Hsueh and Whangee (D. Membranaceus Munro) andtheir physical and mechanical properties have been studied in the paper. The results showed that the whangee hasbetter physi...Two kinds of big sympodial bamboo, D.Yunnanicus Hsueh and Whangee (D. Membranaceus Munro) andtheir physical and mechanical properties have been studied in the paper. The results showed that the whangee hasbetter physical properties than that of the Yunnanicus, such as higher density, lower tangential and longitudinal dryshrinkages. That also showed that Whangee has stronger mechanical properties in MOR and MOE, compressivestrength and shear strength parallel to the grain. Compared with some wood species used in architecture, the physicaland mechanical properties of the two kinds have reached the requirement of some wood architecture structurematerials.展开更多
In this paper, the physical and mechanical properties of laminated bamboo lumber were studied by testing moisture content, delamination ratio, horizontal shear strength, MOE and MOR of the structure-use material, in t...In this paper, the physical and mechanical properties of laminated bamboo lumber were studied by testing moisture content, delamination ratio, horizontal shear strength, MOE and MOR of the structure-use material, in the same time, these subjects of finger-joint were tested too. The results showed that, the horizontal shear strength, MOR, MOE of laminated bamboo were superior to the ordinary structure-use timber in architecture, such as Pinus. The performance of aging test was not extraordinary, although the physical and mechanical properties of laminated bamboo lumber decreased after aging test, these properties were beyond Pinus yet.展开更多
文摘The properties of anti-seismic HRB400 steel bars with 25 mm diameter were systematically investigated. The results showed that the properties of the HRB400 reinforced steel bars had been greatly enhanced comparing with HRB335 steel bars, i.e. coordination of strength and ductility, strain-aging sensibility, low temperature impact toughness, weld ability and high strain low cycle fatigue. The ductile-brittle transit temperatures of hot-rolled and strain-aged steel bars were evaluated as –17 °C and ?8 °C respectively, and the low temperature impact toughness of HRB400 steel bars remains to be improved. Transmission electron microscopy (TEM) and electron diffraction showed little vanadium existed in ferrite as VN, most of which existed in pearlite as alloy cementite which resulted in the declination of impact toughness. Methods were suggested to improve the anti- seismic properties of steel bars.
文摘Green cutting has become focus of attention in ecological and environmental protection. Steam is cheap, poilution-free and eco-friendly, and then is a good and economical coolant and lubricant. Steam generator and steam feeding system were developed to generate and feed steam. Comparative experiments were carried out in cutting AA6061-15 vol.% SiC （25 p.m particle size）, with cubic boron nitride （CBN） insert KB-90 grade under the conditions of compressed air, oil water emulsion, steam as coolant and lubricant, and dry cutting, respectively. The experimental results show that, with steam as coolant and lubricant, gradual reduction in the cutting force, friction coefficient, surface roughness and cutting temperature values were observed. Further, there was reduction in built up edge formation. It is proved that use of water steam as coolant and lubricant is environmentally friendly.
文摘A number of geotechnical analyses were carried out on selected carbonate rock samples from eight sites located in Egypt. This analysis was to assess the suitability of these rocks for building construction aggregate. The analyses included properties of uniaxial compressive strength, tensile strength, porosity, water absorption, and dynamic fragmentation. The success of building construction depends to a large extent on the availability of raw materials at affordable prices. Raw materials commonly used in the building industry include sands, gravels, clays and clay-derived products. Despite the widespread occurrence of carbonate rocks throughout Egypt, the low premium placed on their direct application in the building sector may be explained in two ways: firstly, the lack of awareness of the potential uses of carbonate rocks in the building construction industry(beyond the production of asbestos, ceiling boards, roof sheets and Portland cement); and secondly, the aesthetic application of carbonate rocks in the building construction depends mainly on their physical attributes, a knowledge of which is generally restricted to within the confines of research laboratories and industries. Thus this paper addresses the physical and mechanical characteristics of some Egyptian carbonate rocks, evaluating them for their suitability as building construction aggregates.
文摘Concrete, as an essential construction material in the construction industry, is the main component of solid waste. To improve the strength and durability of concrete, some additives can be added into concrete to replace parts of cement. Carbon fiber and silica powder are the most common additives. Under a series of experiments, the effects of temperature, carbon fiber and silica powder on the mechanical properties of concrete were studied under normal circumstances. In this paper, a conclusion on the effects was drawn up mainly through some experimental analyses, so as to discuss the effect laws and provide a reference to manufacture the concrete of high strength and properties.
文摘The aim of this research was to find out whether the effect of chemical corrosion changes mechanical characteristics of surface layers of wooden construction elements. Degradation of the surface layers of wood was caused by chemical reactions of the basic substances of wood mass with compounds contained in antifire coatings. Fire retardants containing corrosive substances were often and repeatedly used in the Czech Republic on many wooden building constructions. This process of chemical corrosion is in practise called as ＂surface defibering of wood＂. This contribution presents standard and special experimental methods used for measuring the selected mechanical characteristics （compression strength, tension strength, bending strength, hardness and impact resistance） in the damaged surface layer of wooden construction elements. The material for experimental measuring was a construction element removed from a historical roof （ca 150 years old）. Mechanical characteristics of the surface layer of the defibered element were compared with the values measured in the deeper subsurface layer of non-damaged wood. The results of the experiments proved loss of cohesive strength and decrease of mechanical characteristics of wood only in a thin surface layer.
文摘The paper summarises the results of a questionnaire survey that took place in January 2015 in order to assess the current and prospective standard of the qualification of human resources in machine construction companies in the Czech Republic. The questionnaire survey included 23 small machine construction companies （less than 50 employees）, 24 medium-sized machine construction companies （50-249 employees）, and 53 larger machine construction companies （250 and more employees）. The results of the survey indicated that almost one half （43%） of respondent machine construction company top management members planned to hire new employees this year. In addition, 50% of them confirmed their endeavour to keep the current headcount and a mere 7% of them specified problems that would lead to the dismissal of employees. However, what is bothering machine construction top management members is the lack of qualifications and practical experience of job seekers they have to deal with. The intention of the authors is to define the main reasons and propose possible solutions of this problem within human resource management in machine construction companies.
文摘Two kinds of big sympodial bamboo, D.Yunnanicus Hsueh and Whangee (D. Membranaceus Munro) andtheir physical and mechanical properties have been studied in the paper. The results showed that the whangee hasbetter physical properties than that of the Yunnanicus, such as higher density, lower tangential and longitudinal dryshrinkages. That also showed that Whangee has stronger mechanical properties in MOR and MOE, compressivestrength and shear strength parallel to the grain. Compared with some wood species used in architecture, the physicaland mechanical properties of the two kinds have reached the requirement of some wood architecture structurematerials.
文摘In this paper, the physical and mechanical properties of laminated bamboo lumber were studied by testing moisture content, delamination ratio, horizontal shear strength, MOE and MOR of the structure-use material, in the same time, these subjects of finger-joint were tested too. The results showed that, the horizontal shear strength, MOR, MOE of laminated bamboo were superior to the ordinary structure-use timber in architecture, such as Pinus. The performance of aging test was not extraordinary, although the physical and mechanical properties of laminated bamboo lumber decreased after aging test, these properties were beyond Pinus yet.
