今天我們學習《機械制圖》——點，直線，平面的投影第三部分的内容。今天的主要内容是平面的投影。Today we are studying Mechanical Drawing - Projection of Points, Lines and Planes Part 3. Today's main topic is the projection of planes.

No.1 平面的表示法

No.2 平面對投影面的各種相對位置

（1）一般位置平面的投影特性：它的三個投影都是平面圖形，而且是面積縮小的類似形。傾斜于投影面的平面圖形在該投影面上的正投影必定是這個平面圖形的類似形，這樣的投影特性通常稱為類似性。

（2）投影面垂直面的投影特性：

A.在垂直的投影面上的投影，積聚成直線；它與投影軸的夾角，分别反映平面對另兩投影的真實傾角。

B.在另兩投影面上的投影為面積縮小的類似性。

（3）投影面平行面

A.在平面的投影面上的投影，反映真形。

B.在另兩投影面上的投影，分别積聚成直線，平行于相應的投影軸。

(1) The projective property of the plane of general position: all three of its projections are planar figures and are similar shapes of reduced area. The orthographic projection of a plane figure inclined to the projection plane must be an analogue of this plane figure; such a projective property is usually called similarity.

(2) The projective properties of a perpendicular plane of projection.

A. The projection on the perpendicular projection plane, accumulating into a straight line; its angle with the projection axis, respectively, reflects the true inclination of the plane to the other two projections.

B. The projection on the other two projection planes as an analogy of area reduction.

(3) Projection plane parallel to plane

A. Projection on the projection plane of the plane reflecting the true form.

B. Projection on the other two projection planes that accumulate into straight lines, respectively, parallel to the corresponding projection axes.

No.3 平面的迹線表示法

（1）平面主要用幾何元素表示，也可以用迹線表示。

（2）迹線是平面與投影面的交線。用迹線表示的平面稱為迹線平面。平面與V面，H面，W面的交線，分别稱為正面迹線，水平迹線，側面迹線。

（3）迹線的符号用平面名稱的大寫字母附加投影面名稱的注腳表示。

（4）投影特性：在垂直的投影面上的迹線與這個平面在該投影面上的有積聚性的投影相重合。它與投影軸的夾角，分别反映平面對另兩投影面的真實傾角；在另兩投影面上的迹線，分别垂直于相應的投影軸。

(1) The plane is mainly represented by geometric elements, but can also be represented by traces.

(2) The trace is the line of intersection between the plane and the projection plane. A plane represented by a trace is called a trace plane. The intersection of the plane with the V, H and W planes is called the frontal trace, the horizontal trace and the lateral trace respectively.

(3) The sign of the trace plane is indicated by a footnote with the name of the plane in capital letters attached to the name of the projection plane.

(4) Projection characteristics: a trace on a vertical projection plane coincides with the projection of this plane on that projection plane with accumulation. Its angle with the projection axis reflects the true inclination of the plane to the other two projection planes, respectively; the trace on the other two projection planes is perpendicular to the corresponding projection axis, respectively.

No.4 平面上的點和線

（1）點在平面上，則該點必定在這個平面的一條直線上

（2）直線在平面上，則該直線必定通過這個平面上的兩個點；或者通過這個平面上的一個點，且平行于這個平面上的另一條直線。

(1) If a point is in the plane, the point must be on a line in the plane

(2) A line is in a plane, then the line must pass through two points in that plane; or through a point in that plane and parallel to another line in that plane.

參考資料：文字：百度；圖片：微博；翻譯：百度翻譯

本文由LearningYard新學苑原創，部分圖片文字來自網絡，如有侵權請聯系。

更多精彩资讯请关注tft每日頭條，我们将持续为您更新最新资讯!