英语翻译Properties of materials All materials have their own pro

英语翻译
Properties of materials
All materials have their own properties or characteristics.these properties may be arranged into major groups which include:
Physical properties .mechanical properties .chemical propertier.Thermal properties .electrical and magnetic properties .optical properties .acoustical properties .
physical properties
Physical properties ,for this discussion are restricted to those which describe the basic features of the material .These features are measured or observed without the use of extensive scientific experiments the comon physical properties are size ,shape,density,and porosity.
Size is the overall dimensions of the object .these dimensions ,for most materials ,are given as thickness ,which ,and length or as diameter and length .
Shape is the contour or ouline of the object .contour is given to an object by curved ,notched ,sloped ,or other irregular surfaces .
Density or specific gravity measures the mass of an object the measurement is by weight for a unit or a certain volume .typically ,density is measured by pounds per cubic foot or kilograms per cubic meter of material .density allows the mass of one material to be compared with that of other materials .
Porosity is a measure of voids in the material ,it is generally described as ratio of open pore volume to total volume of a material .this ratio is expressed as a percentage .porosity will provide a mesure of liquid-holding power ,or the ability of air or gas to move through the material .

材料的性能
所有材料都有自己的属性或是特性,这些属性可以大致分成几个大类,其中包括:
物理特性.机械特性.化学特性.热学特性.电磁特性.光学特性.隔音特性.
物理特性
物理特性,仅限于讨论那些描述材料的基本特征.这些基本特点不需要采用大量的科学实验来测量或者观察得到.这些常见的物理性质有：尺寸、形状、密度、孔隙度.
尺寸是一个物体的外廓尺寸（或是综合尺寸）,这些尺寸对于大多数材料来说,是指厚度就如长度或是直径和长度一样.
形状是指一个物体的轮廓或外形.轮廓是通过对物体弯曲,缺口、倾斜、或其他不规则表面的测量获得的.
密度或比重衡量一个物体的质量的大小.测量是以质量为一个基本单位或为一个定量.很典型的,密度是以磅每立方英尺或公斤/立方米的材料来测量的.密度可以作为一个材料同其他材料比较的质量依据.
孔隙度是衡量材料中的空隙数,通常是指开孔量占总容积率的比值.孔隙度是以百分比表示的.孔隙度能表示材料储水的能力,或时气体液体通过材料的能力.
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