The wear patterns for drum-style automotive brakes tend to enlarge internal drum diameters. Such enlargement is most profound when used brake drums are machined to restore the metal friction surfaces. Specialized arc ...The wear patterns for drum-style automotive brakes tend to enlarge internal drum diameters. Such enlargement is most profound when used brake drums are machined to restore the metal friction surfaces. Specialized arc grinding machinery has been used to match replacement shoe-style brake friction materials to enlarged drums. The process of arc grinding removes friction material, thereby producing dust. When organic-style friction materials contained asbestos, use of arc grinding machinery posed an asbestos fiber exposure risk to operators and proximate personnel. The manufacturers of arc grinding machinery have incorporated local exhaust ventilation systems designed to capture and remove this dust at the point of grinding contact and propel this dust into collection bags or other systems. This research was designed to evaluate the dust capture and retention characteristics of a specific arc grinder product, when used to custom grind asbestos-containing brake friction materials. A Bear Model 1420 automotive brake shoe arc grinder was the subject of this study. During two separate but consecutive test sessions, newly relined sets of shoe-style automobile brake friction materials were precision ground. Both area and personal air samples were collected throughout each testing session. This work took place within a closed and unventilated metal building, with total interior volume of 2500 m<sup>3</sup>. Collected air samples were analyzed using phase contrast microscopy (PCM) and transmission electron microscopy (TEM). The results of analysis using PCM for personal samples (n = 6) ranged from <0.044 to 0.055 fibers per cc (f/cc) (mean 0.05). Follow-up analysis of these personal samples using TEM indicated asbestos-adjusted PCM exposures ranging from <0.0074 to 0.055 f/cc (mean ≤ 0.041). Area air samples, taken at distances ranging from 1.5 to 9 meters from the arc grinder (n = 12), showed asbestos-adjusted PCM concentrations ranging from <0.0075 to 0.041 f/cc (mean ≤ 0.017). The process of custom arc grinding shoe-style, asbestos-containing brake friction materials can cause exposure to airborne asbestos fibers. However, when done using properly equipped arc grinding machines, such exposures are not expected to exceed the current occupational exposure limits for asbestos of 0.1 f/cc 8-hour time-weighted average (TWA) or 1.0 f/cc 30-minute average.展开更多
电感储能型脉冲电源是目前电磁发射技术的研究热点,提升装置储能密度对于推动电感储能型脉冲电源的应用和研究具有重要意义。本文介绍了一种适用于电感储能型脉冲电源的名为meat grinder with SECT的新电路,并对该电路进行了详细的原理...电感储能型脉冲电源是目前电磁发射技术的研究热点,提升装置储能密度对于推动电感储能型脉冲电源的应用和研究具有重要意义。本文介绍了一种适用于电感储能型脉冲电源的名为meat grinder with SECT的新电路,并对该电路进行了详细的原理分析,指出该电路兼具电流关断能力强和拓扑结构简单的优点。通过仿真将meat grinder with SECT和STRETCH meat grinder、STRETCH meat grinder with ICCOS这两种主流电路进行了性能比较,发现meat grinder with SECT电路在保持电气性能不变的同时,成本最低,体积最小。基于meat grinder with SECT电路,本文研制了50k J电感储能型脉冲电源并进行了试验测试,测试结果达到了预期目标。展开更多
Considering grinding a cam with numerical control(NC)cam grinder,a mathematical model should be estab- lished with the unified parameter based on the original cam-lobe lift data to describe the movement of wheel and...Considering grinding a cam with numerical control(NC)cam grinder,a mathematical model should be estab- lished with the unified parameter based on the original cam-lobe lift data to describe the movement of wheel and establish the relation between the wheel center coordinate,the measuring angle and workpiece’s spindle rotation angle.By analyzing,the grinding wheel can be regarded as different followers.To the planar and roller followers,different mathematical models are established, but they can be unified in Eqs.(17)of this paper with the different value of the roller radius r<sub>1</sub>.And also the model is suit for the edged follower when assuming the roller radius r<sub>1</sub>=0.Experimental verification was done with TKM120 CNC/CBN grinder with NC sets’ interpolation according to the model,which shows that high precision parts can be manufactured and this mathemat- ical model can be practically applied for NC cam grinder.展开更多
Inductive energy storage systems (IES)require opening switches which are technically much more difficult to realize than closing switches. Institute of Advanced Technology ( IAT ) puts forward a meat grinder with ...Inductive energy storage systems (IES)require opening switches which are technically much more difficult to realize than closing switches. Institute of Advanced Technology ( IAT ) puts forward a meat grinder with an inductive pulse power topology called slow transfer of energy through capacitive hybrid (STRETCH). In this topology, an integrated gate-commutated thyristor (IGCT) is capable of breaking the charging currents on the order of 4 kA, and it may encounter difficulties in expanding to higher energy systems. German-French Institute of Saint Louis (ISL) has developed a high-power opening switch based on standard high-power thyristors by using their so-called inverse current commutation with semiconductor devices (ICCOS) countercurrent commutation principle. Two topologies of the STRETCH meat grinder with ICCOS are analyzed. And they are compared based on the voltage across the main switch, the current multiplication factor and other aspects by u- sing Matlab simulations. The advantages and disadvantages of the two topologies are shown through the comparisons. Therefore a more suitable topology can be chosen for realistic applications accord- ing to their performances.展开更多
The 40-year-old Hangzhou MachineTools Works is a special manufacturerof surface grinders. It produces sevenseries with 120 specifications of varioussurface grinders. In addition to meetingdomestic demand, its products...The 40-year-old Hangzhou MachineTools Works is a special manufacturerof surface grinders. It produces sevenseries with 120 specifications of varioussurface grinders. In addition to meetingdomestic demand, its products have beenexported to some 60 countries and regions,including the USA, the UK, Germany andJapan. The M7150HX10 is one of its exportproducts.展开更多
The S7520A universal thread grinder, made by the Shaanxi Hanjiang Machine Tool Plant. is used in grinding various precision threads and precision screws. It is suitable for use in tool workshops of machine manufacturers
Purpose: To investigate whether long-term noise exposure affects the cognitive ability of grinders. Methods: Cumulative noise exposure (CNE) and LAeq.8h determination were used to characterize the level of individual ...Purpose: To investigate whether long-term noise exposure affects the cognitive ability of grinders. Methods: Cumulative noise exposure (CNE) and LAeq.8h determination were used to characterize the level of individual noise exposure;the Montreal Cognitive Assessment (MoCA) test (Beijing version) was used to evaluate cognitive function. Results: We compared the basic situation of workers in different groups and individual noise exposure intensity of grinders was monitored. Multiple linear-regression analysis was made and score of MoCA in different group was finally drawn. Conclusion: CNE and total score of MoCA have the relationship of negative correlation (r = -0.303, p < 0.05) which means long-term occupational noise exposure can affect the cognitive ability of grinders.展开更多
Six-axis numerical control spiral bevel gear grinder was taken as the object, multi-body system theory and Denavit-Hartenberg homogeneous transformed matrix (HTM) were utilized to establish the grinder synthesis error...Six-axis numerical control spiral bevel gear grinder was taken as the object, multi-body system theory and Denavit-Hartenberg homogeneous transformed matrix (HTM) were utilized to establish the grinder synthesis error model, and the validity of model was confirmed by the experiment. Additionally, in grinding wheel tool point coordinate system, the errors of six degrees of freedom were simulated when the grinding wheel revolving around C-axis, moving along X-axis and Y-axis. The influence of these six errors on teeth space, helix angle, pitch, teeth profile was discussed. The simulation results show that the angle error is in the range from -0.148 4 rad to -0.241 9 rad when grinding wheel moving along X, Y-axis; the translation error is in the range from 0.866 0 μm to 3.605 3 μm when grinding wheel moving along X-axis. These angle and translation errors have a great influence on the helix angle, pitch, teeth thickness and tooth socket.展开更多
The present work emphasizes the isolation of cellulose nanofiber(CNF)from the kenaf(Hibiscus cannabinus)bast through a chemo-mechanical process.In order to develop high CNF yield with superior properties of CNF for im...The present work emphasizes the isolation of cellulose nanofiber(CNF)from the kenaf(Hibiscus cannabinus)bast through a chemo-mechanical process.In order to develop high CNF yield with superior properties of CNF for improving compatibility in varied applications this method is proposed.The fiber purification involved pulping and bleaching treatments,whereas mechanical treatment was performed by grinding and high-pressure treatments.The kraft pulping as a delignification method followed by bleaching has successfully removed almost 99%lignin in the fiber with high pulp yield and delignification selectivity.The morphology of the fibers was characterized by scanning electron microscopy,which showed a smooth surface,fiber bundles,gel-shaped nanofiber,and an average size of 94.05 nm with 69%of CNF in 34–100 nm size.The chemo-mechanical process exhibited a more crystalline nature in CNF than pulp kenaf.The low zeta potential values exhibit the distribution of fibrils and colloidal suspension stability without any further agglomeration.A lower concentration of CNF is less stable exhibiting the product agglomeration.Therefore,the chemo-mechanical process for the isolation of CNF(Hibiscus cannabinus)from kenaf involves sustainable,low-cost,non-toxic,and cheap alternatives than other traditional methods.展开更多
文摘The wear patterns for drum-style automotive brakes tend to enlarge internal drum diameters. Such enlargement is most profound when used brake drums are machined to restore the metal friction surfaces. Specialized arc grinding machinery has been used to match replacement shoe-style brake friction materials to enlarged drums. The process of arc grinding removes friction material, thereby producing dust. When organic-style friction materials contained asbestos, use of arc grinding machinery posed an asbestos fiber exposure risk to operators and proximate personnel. The manufacturers of arc grinding machinery have incorporated local exhaust ventilation systems designed to capture and remove this dust at the point of grinding contact and propel this dust into collection bags or other systems. This research was designed to evaluate the dust capture and retention characteristics of a specific arc grinder product, when used to custom grind asbestos-containing brake friction materials. A Bear Model 1420 automotive brake shoe arc grinder was the subject of this study. During two separate but consecutive test sessions, newly relined sets of shoe-style automobile brake friction materials were precision ground. Both area and personal air samples were collected throughout each testing session. This work took place within a closed and unventilated metal building, with total interior volume of 2500 m<sup>3</sup>. Collected air samples were analyzed using phase contrast microscopy (PCM) and transmission electron microscopy (TEM). The results of analysis using PCM for personal samples (n = 6) ranged from <0.044 to 0.055 fibers per cc (f/cc) (mean 0.05). Follow-up analysis of these personal samples using TEM indicated asbestos-adjusted PCM exposures ranging from <0.0074 to 0.055 f/cc (mean ≤ 0.041). Area air samples, taken at distances ranging from 1.5 to 9 meters from the arc grinder (n = 12), showed asbestos-adjusted PCM concentrations ranging from <0.0075 to 0.041 f/cc (mean ≤ 0.017). The process of custom arc grinding shoe-style, asbestos-containing brake friction materials can cause exposure to airborne asbestos fibers. However, when done using properly equipped arc grinding machines, such exposures are not expected to exceed the current occupational exposure limits for asbestos of 0.1 f/cc 8-hour time-weighted average (TWA) or 1.0 f/cc 30-minute average.
文摘电感储能型脉冲电源是目前电磁发射技术的研究热点,提升装置储能密度对于推动电感储能型脉冲电源的应用和研究具有重要意义。本文介绍了一种适用于电感储能型脉冲电源的名为meat grinder with SECT的新电路,并对该电路进行了详细的原理分析,指出该电路兼具电流关断能力强和拓扑结构简单的优点。通过仿真将meat grinder with SECT和STRETCH meat grinder、STRETCH meat grinder with ICCOS这两种主流电路进行了性能比较,发现meat grinder with SECT电路在保持电气性能不变的同时,成本最低,体积最小。基于meat grinder with SECT电路,本文研制了50k J电感储能型脉冲电源并进行了试验测试,测试结果达到了预期目标。
文摘Considering grinding a cam with numerical control(NC)cam grinder,a mathematical model should be estab- lished with the unified parameter based on the original cam-lobe lift data to describe the movement of wheel and establish the relation between the wheel center coordinate,the measuring angle and workpiece’s spindle rotation angle.By analyzing,the grinding wheel can be regarded as different followers.To the planar and roller followers,different mathematical models are established, but they can be unified in Eqs.(17)of this paper with the different value of the roller radius r<sub>1</sub>.And also the model is suit for the edged follower when assuming the roller radius r<sub>1</sub>=0.Experimental verification was done with TKM120 CNC/CBN grinder with NC sets’ interpolation according to the model,which shows that high precision parts can be manufactured and this mathemat- ical model can be practically applied for NC cam grinder.
文摘Inductive energy storage systems (IES)require opening switches which are technically much more difficult to realize than closing switches. Institute of Advanced Technology ( IAT ) puts forward a meat grinder with an inductive pulse power topology called slow transfer of energy through capacitive hybrid (STRETCH). In this topology, an integrated gate-commutated thyristor (IGCT) is capable of breaking the charging currents on the order of 4 kA, and it may encounter difficulties in expanding to higher energy systems. German-French Institute of Saint Louis (ISL) has developed a high-power opening switch based on standard high-power thyristors by using their so-called inverse current commutation with semiconductor devices (ICCOS) countercurrent commutation principle. Two topologies of the STRETCH meat grinder with ICCOS are analyzed. And they are compared based on the voltage across the main switch, the current multiplication factor and other aspects by u- sing Matlab simulations. The advantages and disadvantages of the two topologies are shown through the comparisons. Therefore a more suitable topology can be chosen for realistic applications accord- ing to their performances.
文摘The 40-year-old Hangzhou MachineTools Works is a special manufacturerof surface grinders. It produces sevenseries with 120 specifications of varioussurface grinders. In addition to meetingdomestic demand, its products have beenexported to some 60 countries and regions,including the USA, the UK, Germany andJapan. The M7150HX10 is one of its exportproducts.
文摘The S7520A universal thread grinder, made by the Shaanxi Hanjiang Machine Tool Plant. is used in grinding various precision threads and precision screws. It is suitable for use in tool workshops of machine manufacturers
文摘Purpose: To investigate whether long-term noise exposure affects the cognitive ability of grinders. Methods: Cumulative noise exposure (CNE) and LAeq.8h determination were used to characterize the level of individual noise exposure;the Montreal Cognitive Assessment (MoCA) test (Beijing version) was used to evaluate cognitive function. Results: We compared the basic situation of workers in different groups and individual noise exposure intensity of grinders was monitored. Multiple linear-regression analysis was made and score of MoCA in different group was finally drawn. Conclusion: CNE and total score of MoCA have the relationship of negative correlation (r = -0.303, p < 0.05) which means long-term occupational noise exposure can affect the cognitive ability of grinders.
基金Project(2005CB724104) supported by the Major State Basic Research Development Program of ChinaProject(1343-77202) supported by the Graduate Students Innovate of Central South University
文摘Six-axis numerical control spiral bevel gear grinder was taken as the object, multi-body system theory and Denavit-Hartenberg homogeneous transformed matrix (HTM) were utilized to establish the grinder synthesis error model, and the validity of model was confirmed by the experiment. Additionally, in grinding wheel tool point coordinate system, the errors of six degrees of freedom were simulated when the grinding wheel revolving around C-axis, moving along X-axis and Y-axis. The influence of these six errors on teeth space, helix angle, pitch, teeth profile was discussed. The simulation results show that the angle error is in the range from -0.148 4 rad to -0.241 9 rad when grinding wheel moving along X, Y-axis; the translation error is in the range from 0.866 0 μm to 3.605 3 μm when grinding wheel moving along X-axis. These angle and translation errors have a great influence on the helix angle, pitch, teeth thickness and tooth socket.
基金Ministry of Education,Culture,Research and Technology(KEMENDIKBUDRISTEK)Republic of Indonesia,for providing the Research Grant“Basic Research Scheme”No.110/E5/PG.02.00.PL/2023.
文摘The present work emphasizes the isolation of cellulose nanofiber(CNF)from the kenaf(Hibiscus cannabinus)bast through a chemo-mechanical process.In order to develop high CNF yield with superior properties of CNF for improving compatibility in varied applications this method is proposed.The fiber purification involved pulping and bleaching treatments,whereas mechanical treatment was performed by grinding and high-pressure treatments.The kraft pulping as a delignification method followed by bleaching has successfully removed almost 99%lignin in the fiber with high pulp yield and delignification selectivity.The morphology of the fibers was characterized by scanning electron microscopy,which showed a smooth surface,fiber bundles,gel-shaped nanofiber,and an average size of 94.05 nm with 69%of CNF in 34–100 nm size.The chemo-mechanical process exhibited a more crystalline nature in CNF than pulp kenaf.The low zeta potential values exhibit the distribution of fibrils and colloidal suspension stability without any further agglomeration.A lower concentration of CNF is less stable exhibiting the product agglomeration.Therefore,the chemo-mechanical process for the isolation of CNF(Hibiscus cannabinus)from kenaf involves sustainable,low-cost,non-toxic,and cheap alternatives than other traditional methods.
基金supports from the National Natural Science Foundation of China (No.52264030)the Yunnan Fundamental Research Projects,China (No.202201BE070001-048)the Special Fund Projects of Central Government Guiding Local Science and Technology Development,China (No.202107AA110002).