БРАТЬЯ И СЁСТРЫ
ответить на во Вот текст: Drawing consists of pulling metal through a die. One type is wire drawing. The diameter reduction that can be achieved in one die is limited, but several dies in series can be used to get the desired reduction. Sheet metal forming Sheet metal forming is widely used when parts of certain shape and size are needed. It includes forging, bending and shearing. One characteristic of sheet metal forming is that the thickness of the sheet changes little in processing. The metal is stretched just beyond its yield point (2 to 4 percent strain) in order to retain the new shape. Bending can be done by pressing between two dies. Shearing is a cutting operation similar to that used for cloth. Each of these processes may be used alone, but often all three are used on one part. For example, to make the roof of an automobile from a flat sheet, the edges are gripped and the piece pulled in tension over a lower die. Next an upper die is pressed over the top, finishing the forming operation, and finally the edges are sheared off to give the final dimensions. Forging Forging is the shaping of a piece of metal by pushing with open or closed dies. It is usually done hot in order to reduce the required force and increase the metal's plasticity. Open-die forging is usually done by hammering a part between two flat faces. It is used to make parts that are too big to be formed in a closed die or in cases where only a few parts are to be made. The earliest forging machines lifted a large hammer that was then dropped on the workpiece, but now air or steam hammers are used, since they allow greater control over the force and the rate of forming. The part is shaped by moving or turning it between blows. Closed-die forging is the shaping of hot metal within the walls of two dies that come together to enclose the workpiece on all sides. The process starts with a rod or bar cut to the length needed to fill the die. Since large, complex shapes and large strains are involved, several dies may be used to go from the initial bar to the final shape. With closed dies, parts can be made to close tolerances so that little finish machining is required. Two closed-die forging operations are given special names. They are upsetting and coining. Coining takes its name from the final stage of forming metal coins, where the desired imprint is formed on a metal disk that is pressed in a closed die. Coining involves small strains and is done cold. Upsetting involves a flow of the metal back upon itself. An example of this process is the pushing of a short length of a rod through a hole, clamping the rod, and then hitting the exposed length with a die to form the head of a nail or bolt.
2) Much of the equipment in the office needs updating.
3) A car is a means of transport.
4) How many cigarettes do you smoke a day?
5) When I got to the theatre, they were already playing the second act.
6) Unusual facts, marvels are called phenomena.
7) The brown sweater is the best.
8) That was the most interesting movie I have ever seen.
9) Uncle Carl is really a sweet old man.
10) Which is the longest river, the Dnipro or the Dnister?
11) Fanny can sew dresses so well.
12) Taras drives dangerously.
13) Those apples look delicious. May I have one?
14) She often sneaks out of the house quietly.
15) I absolutely refuse to stay here any longer.
Muscle Contraction: Muscles are made up of bundles of individual muscle fibers. When these muscle fibers receive signals from the nervous system, they contract, which means they shorten and generate force. This contraction is the primary mechanism by which muscles create movement.
Muscle Groups and Antagonistic Pairs: Muscles often work in groups and pairs to create coordinated movements. For example, when you bend your arm at the elbow, the biceps muscle contracts, while the triceps muscle relaxes. These muscles are known as antagonistic pairs, as they have opposing actions.
Tendons and Bones: Muscles are attached to bones via tendons, which are strong connective tissues. When a muscle contracts, it pulls on the attached tendon, which, in turn, pulls on the bone, causing movement around the joint.
Muscle Fiber Types: Our muscles consist of different types of muscle fibers, including slow-twitch fibers and fast-twitch fibers. Slow-twitch fibers are responsible for endurance activities and sustained contractions, while fast-twitch fibers generate more force and are involved in quick, powerful movements.
Muscle Synergies: Multiple muscles often work together in a coordinated manner to perform complex movements. These muscle synergies involve the activation and synchronization of various muscle groups to produce smooth and efficient motions.
Fine Motor Control: In addition to larger movements, our muscles also enable fine motor control. Small, intricate movements, such as typing on a keyboard or holding a pen, require precise coordination of muscles and motor units to execute precise actions.