英文.doc

薄板与板材的弯曲

收藏

压缩包内文档预览:
预览图 预览图 预览图
编号:6084920    类型:共享资源    大小:431.51KB    格式:RAR    上传时间:2017-11-11 上传人:闰*** IP属地:河南
13
积分
关 键 词:
薄板 板材 弯曲 曲折
资源描述:
薄板与板材的弯曲,薄板,板材,弯曲,曲折
内容简介:
Sheet and Plate BendingBending is a method of producing shapes by stressing metal beyond its yield strength, but not past its ultimate tensile strength. The forces applied during bending are in opposite directions, just as in the cutting of sheet metal. Bending forces , however, are spread farther apart, resulting in plastic distortion of metal without failure.The bending process appears to be simple; yet, in reality, it is a rather complex process involving a number of technical factor. Included are characteristics of the work piece material flow and required to from the bend, and the type if equipment used.In the large, varied field of sheet metal and plate fabricating, several types of bending machines are used. Press brakes predominate in shops that process heavy-gage materials, because they are well suited to such applications and also because they are adaptable to other metalworking operations, such as punching, piercing, blanking, notching, perforating, embossing, shearing, and drawing.Light-gage metal typically is formed with specialized bending machines, which are also described as leaf, pan, or box brakes; as wing folders; and as swivel bender. Equipment of this type is often manually operated.The principal kinds of equipment used to bend sheet metal and plate can be grouped into the following categories: 1. Mechanical press brakes-elongated presses with numerous tooling options. Work is performed by means of energy released from a motor-driven flywheel. These machines normally have a 3” or 4” stroke length.2. Hydraulic press brakesstretched C-frame presses that are likewise compatible with a wide range and diversity of tooling. High-pressure oil in hydraulic cylinders supplies the force, which is directed downward in most models. The stroking length usually exceeds 6”.3. Hydraulic-mechanical press brakespresses with drives that combine hydraulic and mechanical principles. In operation, oil forces a piston to move arms that push the ram toward the bed.4. Pneumatic press brakeslowtonnage bending machines that are available with suitable tooling options.5. Bending brakespowered or manual brakes commonly used for bending ligh-gage sheet metal.6. Special equipmentcustom-built bender and panel formers designed for spwcific firming applications.Bend allowanceBend allowance is the dimensional amount added to a part through elongation during the bending process. It is used as a key factor in determining the initial blank size.The length of the neutral axis or bend allowance is the length of the blank. Since the length of the neutral axis depends upon its position within the bend area, and this position is dictated by the material type and thickness and the radius and degree of bend, it is impossible to use one formula for all conditions. However, for simplicity, a reasonable approximation with sufficient accuracy for practical usage when air bending is given by the following equation:)(2360ktRALor)(1745.twhere:L=bend allowance (arc length of the neutral axis) in. or mmA=bend angle, degR=inside radius of part, in. or mmt=metal thichness, in. or mmk=constant, neutral-axis locationTheoretically, the neutral axis follows a parabolic arc in the bend region; therefore, the k factor is an average value that is sufficiently accurate for practical applications. A value of 0.5 for k places the neutral axis exactly in the center of the metal. This figure is often used for some thicknesses. One manufacturer specifies k according to sheet thichness and inside radius of the bend; when R is less than 2t, k=0.33; when R is 2t or more, k=0.50.Types of bendingThe basic types of bending applicable to sheet metal forming are straight bending, flange bending and contour bending. Straight bending During the forming of a straight bend the inner grains are compressed and the outer grains are elongated in the bend zone. Tensile strain builds up in the outer grains and increases with the decreasing bend radius. Therefore, the minimum bend radius is an important quantity in straight bending since it determines the limit of bending beyond which splitting occurs.Flange Bending Flange bend forming consists of forming shrink and stretch flange as illustrated. This type of bending is normally produced on a hydrostatic or rubber-par press at room temperature for materials such as aluminum and light-gage steel.Parts requiring very little handwork are produced if the flange height and free-form-radius requirements are not severe. However, forming metals with low modulus of elasticity to yield strength ratios, such as magnesium and titanium, may result in undesirable buckling and springback. Also, splitting may result during stretch-flange forming as a function of material elongation. Elevated temperatures utilized during the bending operation enhance part formability and definition by increasing the material ductility and lowering the yield strength, providing less spring back and buckling.Contour Bending Single-contour bending is performed on a three-roll bender or by using special feeding devices with a conventional press brake. Higher production rates are attained using a three-roll bending machine. Contour radii are generally quite large; forming limits are not a factor. However, springback is a factor because of the residual-stress buildup in the part; therefore, overforming is necessary to produce a part within tolerance.Stretch Bending Stretch bending is probably the most sophisticated bending method and requires expensive tooling and machines. Furthermore, stretch bending requires lengths of material beyond the desired shape to permit gripping an
温馨提示:
1: 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
提示  人人文库网所有资源均是用户自行上传分享,仅供网友学习交流,未经上传用户书面授权,请勿作他用。
关于本文
本文标题:薄板与板材的弯曲
链接地址:https://www.renrendoc.com/p-6084920.html

官方联系方式

2:不支持迅雷下载,请使用浏览器下载   
3:不支持QQ浏览器下载,请用其他浏览器   
4:下载后的文档和图纸-无水印   
5:文档经过压缩,下载后原文更清晰   
关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服 - 联系我们

网站客服QQ:2881952447     

copyright@ 2020-2025  renrendoc.com 人人文库版权所有   联系电话:400-852-1180

备案号:蜀ICP备2022000484号-2       经营许可证: 川B2-20220663       公网安备川公网安备: 51019002004831号

本站为文档C2C交易模式,即用户上传的文档直接被用户下载,本站只是中间服务平台,本站所有文档下载所得的收益归上传人(含作者)所有。人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。若文档所含内容侵犯了您的版权或隐私,请立即通知人人文库网,我们立即给予删除!