The influence of skill and low back pain on trunk postures and low back loads of shearers

Shearing is a rural occupation developing considerable spinal loads and carrying a high risk of low back pain (LBP). Although the workforce has a skill structure, interaction between skill, spinal loads and LBP is unknown. We examined whether skill and LBP influenced trunk postures and loads within a sample of 80 shearers representing shear skill levels. A progression from junior to open class demonstrated a 100% increase in productivity, less time in severe flexion, more time in neutral lateral bend, and more time in axially twisted postures, with no increase in cumulative compressive and anterior shear forces. LBP prevalence increased linearly from 10% for junior through to 76% for open class shearers. Shearers with a history of LBP generated greater cumulative right medio-lateral shear forces, greater left lateral bend and left axial twist moments. Skill-based training that reduces asymmetric forces may help reduce such high prevalence levels of LBP.

Statement of Relevance: Shearing is an important and physically demanding rural occupation. It requires sustained flexed postures that generate considerable spinal loads and a high risk of LBP. This research examines how skill and a history of LBP it carries interact to influence trunk postures and spinal loads within a sample of shearers.     

现浇剪力墙结构转换层模板支撑施工技术

结合具体工程实例,对现浇剪力墙结构转换层模板设计进行了探讨,并对梁侧模板、梁模板扣件的钢管支撑进行了计算说明,阐述了混凝土的浇筑顺序,提出了施工质量控制目标,以供类似工程参考应用。     

钢筋混凝土拆除爆破炮孔装药量的确定

本文从分析钢筋混凝土爆破破坏形态出发,对钢筋混凝土的配筋情况,如强度、配筋网规格、钢筋层数等对拆除爆破的影响作了量化处理,在前人的基础上大胆提出了钢筋混凝土加强抛掷爆破的炮孔装药量计算公式,并在实际工程中得到了验证。     

某露天矿区全风化花岗岩原位试验研究

针对南方某露天矿区全风化花岗岩进行现场原位试验,选择制备了3组代表性的全风化花岗岩试体,通过设计堆载对试体加载不同垂直荷载的正应力、水平剪应力,直至剪切破坏的试验,对试验数据整理分析,获得正应力σ和正应变ε曲线图、剪应力τ和剪应变ε曲线图,用最小二乘法回归得出抗剪强度曲线图和C、φ值及相关系数R;根据试验施加的单位压力P和实测的岩体变形S,绘制P-S关系曲线,得出弹性(变形)模量。为采场边坡稳定性计算分析提供更符合实际的岩土力学参数,也为工程中遇到类似的风化花岗岩时提供参考。     

Characterization of mechanically sheared edges of dual phase steels

In recent years advanced high strength steels (AHSS) received increased interest for light structures with improved performance, but they are often sensitive to edge cracking during sheet metal forming. In this study mechanically sheared edges were characterized for three dual phase steels (DP600, DP780 and DP980), sheared with three die clearances (5%t, 10%t, 15%t) and along rolling and transverse directions. Microstructures of the materials were provided first, and then the sheared edges were examined by optical microscopy and scanning electron microscopy that reveal the morphology and random feature of the sheared edges. A factorial analysis was performed to reveal the general trends of the processing parameters on four edge zones. A new strain measurement method was used for characterizing strain distribution in the sheared region, which shows the peak strain to be higher than 3. The strain quickly decreases from sheared edge to interior, leaving a shear-affected zone of about 500 μm or 31% of the thickness. The fracture processes and involved mechanisms were discussed.     

浮动式液压剪的结构特点及参数计算

本文结合作者的浮动式液压剪的设计、调试体会,分析了液压剪的结构组成,并对液压剪设计所需的一些重要参数进行确定。     

Effect of periodic melt shearing process and cooling rate on structure and hardness of Al–0.7Fe aluminum alloy

In this investigation, the effect of periodic melt shearing process and cooling rate on an Al–Fe alloy was studied. Microstructural examinations were conducted by X-ray diffraction, optical and scanning electron microscopy coupled with energy dispersive spectrometry (EDS). Experimental results suggest that shearing above melting point can refine the alloy structure and improve the morphology of intermetallic phases and; the level of refinement is increased by increase of shearing time. Also, increasing cooling rate through reduced sections, decreases grain size and secondary dendrite arm spacing (SDAS) and improves the microstructure of Al–Fe alloy. The results of hardness test showed that increasing cooling rate and time of melt shearing reduce the hardness of Al–Fe alloy.     

锆-钛-钢复合板界面损伤机理及表面耐腐蚀性能

运用内聚力模型研究了锆-钛-钢复合板在粘结试验中的界面损伤过程,并利用扫描电子显微镜分析了界面断裂机理。运用正交试验研究了不同热处理工艺条件下的表面耐腐蚀性能,分析了保温温度、保温时间和升降温速率对粘结性能的影响。结果表明,I型裂纹加载下,界面损伤由内壁处开始,并逐渐发展至整个界面。界面整体属于脆性断裂,而波峰与波谷的过渡斜面则为混合断裂。腐蚀试验的塔菲尔极化曲线研究结果表明,锆覆层在HCl溶液中以点腐蚀为主,而在HAc溶液中以均匀腐蚀为主。爆炸焊接后,锆复合板的耐点腐蚀性能低于纯锆材料,并且保温温度越高,保温时间越长,耐腐蚀性能下降越明显。     

粘钢加固混凝土的抗剪强度试验研究

在采用不同界面剂和有无螺栓锚固的处理下,研究了钢板和混凝土试块界面粘结抗剪强度。试验包括12组互为对比的粘钢混凝土试块,分析了不同界面剂、有无螺栓锚固和龄期三种因素对粘结界面抗剪强度的影响。试验结果表明:界面剂的种类对界面粘结抗剪强度影响较大;螺栓锚固对采用不同的界面剂抗剪强度的提高效果不一;随着龄期的增长,有利于提高磷酸钾镁水泥试件组的界面粘结抗剪强度,但对另外两种界面剂试件组的抗剪强度影响不大。     

Ni-Ti形状记忆合金侵彻变形与断裂研究

研究了Ni-Ti形状记忆合金在高速冲击条件下的侵彻过程。利用光学显微镜对Ni-Ti形状记忆合金在高速冲击后的微观组织进行考察,分析Ni-Ti合金板材的损伤和断裂。结果表明:奥氏体相为基的Ni-Ti形状记忆合金板材,在高速冲击过程中,发生应力诱发马氏体相变;板材内形成剪切带、微裂纹等形式的损伤,导致材料发生变形和破坏;裂纹按着微孔洞聚集型机制扩展。